Production method of lithuim secondary battery and production device therefor

ABSTRACT

A manufacturing method of the present invention includes ejecting a melt  61  of a solid electrolyte onto at least one electrode plate selected from a positive electrode plate  20  and a negative electrode plate  30,  thereby depositing the melt  61  onto the at least one electrode plate, and compressing the positive electrode plate  20  and the negative electrode plate  30  while sandwiching the melt  61,  thereby forming a layered body including the positive electrode plate  20,  an electrolyte layer  62  including the solid electrolyte, and the negative electrode plate  30.  In accordance with this manufacturing method, a thin lithium secondary battery having excellent characteristics can be manufactured in a highly productive manner.

TECHNICAL FIELD

[0001] The present invention relates to a method for manufacturing alithium secondary battery and an apparatus for manufacturing the same.

BACKGROUND ART

[0002] A lithium secondary battery includes a solid electrolyte, andpositive and negative electrodes that are arranged so as to sandwich thesolid electrolyte. Accompanying the recent trend toward thinner lithiumsecondary batteries, it has become necessary to reduce the thickness ofa solid electrolyte. As a method for reducing a solid electrolytethickness, a deposition technique can be considered.

[0003] However, because of the complex composition of the solidelectrolyte used for the lithium secondary batteries, a solidelectrolyte with excellent characteristics cannot be formed easily bythe deposition technique. Further, there has been a problem that thedeposition technique cannot be carried out with sufficient productivity.

DISCLOSURE OF INVENTION

[0004] With the foregoing in mind, it is an object of the presentinvention to provide a method for manufacturing a thin lithium secondarybattery with excellent characteristics in a highly productive manner,and an apparatus for manufacturing the same.

[0005] In order to achieve the above-mentioned object, a manufacturingmethod of the present invention is a method for manufacturing a lithiumsecondary battery including a positive electrode plate, a negativeelectrode plate, and a solid electrolyte arranged between the positiveelectrode plate and the negative electrode plate. The method includes

[0006] (i) ejecting a melt of the solid electrolyte onto at least oneelectrode plate selected from the positive electrode plate and thenegative electrode plate, thereby depositing the melt onto the at leastone electrode plate, and

[0007] (ii) compressing the positive electrode plate and the negativeelectrode plate while sandwiching the melt, thereby forming a layeredbody including the positive electrode plate, an electrolyte layerincluding the solid electrolyte, and the negative electrode plate. Withthis manufacturing method of the present invention, since a thin solidelectrolyte layer having excellent characteristics can be formed in ahighly productive manner, a thin lithium secondary battery havingexcellent characteristics can be manufactured in a highly productivemanner.

[0008] In the above-described manufacturing method, the solidelectrolyte may contain Li₃PO₄. In this case, the solid electrolyte maybe Li₃PO₄, a solid electrolyte obtained by adding nitrogen to Li₃PO₄, orLi₃PO₄—Li₂S—SiS₂.

[0009] The above-described manufacturing method further may includeafter the (ii) compressing,

[0010] (iii) layering the layered body by ejecting the melt of the solidelectrolyte onto at least one surface of the layered body and thenwinding the layered body.

[0011] In the above-described manufacturing method, in the (ii)compressing, the layered body may be formed by compressing the positiveelectrode plate and the negative electrode plate while cooling themdown. With this configuration, it is possible to manufacture a lithiumsecondary battery having particularly excellent characteristics.

[0012] In the above-described manufacturing method, the electrolytelayer may have a thickness ranging from 0.1 μm to 10 μm.

[0013] Further, a manufacturing apparatus of the present invention is anapparatus for manufacturing a lithium secondary battery including apositive electrode plate, a negative electrode plate, and a solidelectrolyte arranged between the positive electrode plate and thenegative electrode plate. The apparatus includes a spraying device forejecting a melt of the solid electrolyte onto at least one electrodeplate selected from the positive electrode plate and the negativeelectrode plate, and a compressing device for compressing the positiveelectrode plate and the negative electrode plate while sandwiching themelt.

[0014] In the above-described manufacturing apparatus, the compressingdevice may include two rollers.

BRIEF DESCRIPTION OF DRAWINGS

[0015]FIG. 1A is a schematic view showing a configuration of an exampleof a manufacturing apparatus for manufacturing a lithium secondarybattery, according to the present invention. Also, FIG. 1B is asectional view schematically showing a main portion of an example of aspraying device used in the manufacturing apparatus of FIG. 1A.

[0016]FIG. 2 is a schematic view showing a configuration of anotherexample of the manufacturing apparatus for manufacturing a lithiumsecondary battery according to the present invention.

[0017]FIG. 3 is a schematic view showing a partial configuration of yetanother example of the manufacturing apparatus for manufacturing alithium secondary battery according to the present invention.

[0018]FIG. 4 is a schematic view showing a partial configuration of yetanother example of the manufacturing apparatus for manufacturing alithium secondary battery according to the present invention.

[0019]FIGS. 5A to 5D are sectional views showing a process flow of anexample of a manufacturing method for manufacturing a lithium secondarybattery according to the present invention.

[0020]FIGS. 6A to 6D are sectional views showing a process flow ofanother example of the manufacturing method for manufacturing a lithiumsecondary battery according to the present invention.

[0021]FIG. 7 is a partially exploded sectional view showing an exampleof a lithium secondary battery to be manufactured according to themanufacturing method of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0022] The following is a description of embodiments of the presentinvention, with reference to the accompanying drawings.

[0023] (First Embodiment)

[0024] The first embodiment is directed to an example of a manufacturingapparatus for manufacturing a lithium secondary battery, according tothe present invention. FIG. 1A schematically shows a configuration of amanufacturing apparatus 10 of the first embodiment.

[0025] Referring to FIG. 1A, the manufacturing apparatus 10 includes afeed roller 11 for sending out a positive electrode plate 20, a feedroller 12 for sending out a negative electrode plate 30, cooling rollers13 and 14, a spraying device 15, and a take-up roller 16. The positiveelectrode plate 20 and the negative electrode plate 30 are wound aroundthe feed roller 11 and the feed roller 12, respectively.

[0026] The spraying device 15 ejects a melt of a solid electrolytetoward the positive electrode plate 20 and the negative electrode plate30. Incidentally, although FIG. 1A illustrates the case of ejecting themelt toward both of the positive electrode plate 20 and the negativeelectrode plate 30, the melt may be ejected toward only one of them.

[0027] The rollers 13 and 14 function as devices for compressing thepositive electrode plate 20 and the negative electrode plate 30, towhich the melt of the solid electrolyte has been ejected, whilesandwiching the melt. The cooling rollers 13 and 14 also may have afunction of cooling down the ejected melt of the solid electrolyterapidly via the positive electrode plate 20 and the negative electrodeplate 30. The take-up roller 16 takes up a layered body of the positiveelectrode plate, a solid electrolyte layer and the negative electrodeplate.

[0028]FIG. 1B shows the configuration of a main portion of an example ofthe spraying device 15. The spraying device 15 includes an anode 151, acathode 152, a nozzle 153 and a RF induction coil 154. A material gas ofplasma is allowed to flow between the anode 151 and the cathode 152, anda high-temperature plasma 155 is generated by the RF induction coil 154.This plasma 155 is discharged from the tip of the nozzle 153. A lateralside of the nozzle 153 is provided with a through hole 156, throughwhich solid electrolyte powder is supplied. This powder is dissolved inthe plasma 155, and its melt is ejected toward the electrode plates.Incidentally, the plasma spraying device illustrated in FIG. 1B ismerely an example, and spraying devices other than the plasma sprayingdevice may be used.

[0029] A method for manufacturing a lithium secondary battery using themanufacturing apparatus 10 will be described in the second embodiment.

[0030] The manufacturing apparatus of the present invention further mayinclude a second spraying device, a positive electrode plate formingdevice or a negative electrode plate forming device. FIG. 2 illustratesa manufacturing apparatus 10 a including a second spraying device 15 a.Further, FIG. 3 illustrates a positive electrode plate forming device40, and FIG. 4 illustrates a negative electrode plate forming device 50.

[0031] Referring to FIG. 2, the manufacturing apparatus 10 a isdifferent from the manufacturing apparatus 10 in that the sprayingdevice 15 a is provided between the take-up roller 16 and the coolingrollers 13 and 14. The spraying device 15 a also ejects the melt of thesolid electrolyte as the spraying device 15 and may be the same as thespraying device 15. By using the manufacturing apparatus 10 a, it ispossible to manufacture a lithium secondary battery in which a pluralityof the positive electrode plates, the solid electrolytes and thenegative electrode plates are layered. A method for manufacturing alithium secondary battery using the manufacturing apparatus 10 a will bedescribed in the second embodiment.

[0032] Referring to FIG. 3, the positive electrode plate forming device40 includes a feed roller 41, rollers 42 and 43, a take-up roller 44 anda deposition device 45. The feed roller 41 sends out a collector 21 ofthe positive electrode. The deposition device 45 deposits an activematerial for positive electrode onto the collector 21. Incidentally,although FIG. 3 illustrates the case of forming an active material layeron both surfaces of the collector 21 using the rollers 42 and 43, italso may be possible to form the active material layer only on onesurface of the collector 21. Further, the active material layer also maybe applied to the collector 21 by an applicator.

[0033] The positive electrode plate 20 a obtained by forming the activematerial layer on both surfaces of the collector 21 is taken up by thetake-up roller 44. It is preferable that the positive electrode plate 20a taken up by the take-up roller 44 is annealed in an annealing furnace46. The manufacturing apparatus 10 of the present invention may includethe positive electrode plate forming device 40 in which the annealingfurnace 46 is integrated, instead of the feed roller 11.

[0034] Referring to FIG. 4, the negative electrode plate forming device50 includes a feed roller 51, rollers 52 and 53, a take-up roller 54 anda deposition device 55. The feed roller 51 sends out a collector 31 ofthe negative electrode. The deposition device 55 deposits an activematerial for negative electrode onto the collector 31. Incidentally,although FIG. 4 illustrates the case of forming an active material layeron both surfaces of the collector 31 using the rollers 52 and 53, italso may be possible to form the active material layer only on onesurface of the collector 31. Further, the active material layer also maybe applied to the collector 31 by an applicator.

[0035] The negative electrode 30 a obtained by forming the activematerial layer on both surfaces of the collector 31 is taken up by thetake-up roller 54. The manufacturing apparatus 10 of the presentinvention may include the negative electrode plate forming device 50instead of the feed roller 12.

[0036] (Second Embodiment)

[0037] The second embodiment is directed to an example of amanufacturing method for manufacturing a lithium secondary battery,according to the present invention. Although the second embodiment willdiscuss the case of using the manufacturing apparatus described in thefirst embodiment, the manufacturing method of the present invention isnot limited to this. FIGS. 5A to 5D show a manufacturing process in thesecond embodiment.

[0038] First, a positive electrode plate 20 as shown in FIG. 5A and anegative electrode plate 30 as shown in FIG. 5B are prepared. Thepositive electrode plate 20 includes a collector 21 and an activematerial layer 22 formed on one surface of the collector 21. It shouldbe noted that the active material layer 22 also may be formed on bothsurfaces of the collector 21. The collector 21 and the active materiallayer 22 can be those generally used for a lithium secondary battery.For example, the collector 21 can be a collector formed of anelectrically conductive material, more specifically, platinum,platinum/palladium, gold, silver, aluminum, copper, nickel, stainlesssteel, ITO (indium-tin oxide film), carbon materials or the like.Further, the active material layer 22 can be a layer containing, forexample, LiCoO₂ or LiNiO₂. The positive electrode plate 20 can be formedby applying or depositing a material of the active material layer 22onto the collector 21.

[0039] The negative electrode plate 30 includes a collector 31 and anactive material layer 32 formed on one surface of the collector 31. Itshould be noted that the active material layer 22 also may be formed onboth surfaces of the collector 21. The collector 31 and the activematerial layer 32 can be those generally used for a lithium secondarybattery. For example, the collector 31 can be similar to the collector21. Also, the active material layer 32 can be a layer containing, forexample, Li and/or C (carbon). More specifically, a layer containing Li,a graphite-based material or a difficult-to-graphitize carbon materialas the active material can be used as the active material layer 32. Thenegative electrode plate 30 can be formed by applying or depositing amaterial of the active material layer 32 onto the collector 31.

[0040] Next, a melt of a solid electrolyte is ejected toward at leastone electrode plate selected from the positive electrode plate 20 andthe negative electrode plate 30, thereby depositing the melt of thesolid electrolyte onto the at least one electrode plate (Process (i)).FIG. 5C illustrates an example of this Process (i). In the exampleillustrated in FIG. 5C, a melt 61 of the solid electrolyte is ejectedtoward and deposited onto both of the positive electrode plate 20 andthe negative electrode plate 30. The melt 61 is deposited onto the sideprovided with the active material layer in the positive electrode plate20 and the negative electrode plate 30.

[0041] The solid electrolyte serving as a material of the melt 61 can bea solid electrolyte that is capable of constituting a lithium secondarybattery and being deposited onto the electrode plate by spraying. Morespecifically, the solid electrolyte to be the melt 61 can be a materialhaving an electron conductivity so small as to be negligible and ionconductivity. Here, it is preferable to use a solid electrolyte havingan excellent lithium ion conductivity because lithium ions are mobileions. In particular, a solid electrolyte containing Li₃PO₄ ispreferable, and for example, Li₃PO₄ or a solid electrolyte obtained byadding nitrogen to Li₃PO₄ (or by substituting a part of elements inLi₃PO₄ with nitrogen, LIPON: represented by a compositionLi_(2.9)PO_(3.3)N_(0.36)) is effective. Similarly, a sulfide solidelectrolyte such as Li₂S—SiS₂, Li₂S—P₂S₅ or Li₂S—B₂S₃ also is effective.Furthermore, a solid electrolyte obtained by doping these solidelectrolytes with lithium halide such as LiI or oxyate containinglithium such as Li₃PO₄ also is effective. For example, Li₃PO₄—Li₂S—SiS₂,which is a mixture of Li₃PO₄, Li₂S and SiS₂, is effective. These solidelectrolytes can be sprayed using a general plasma spraying device orthe like.

[0042] After the melt 61 is deposited, the positive electrode plate 20and the negative electrode plate 30 are compressed while sandwiching themelt 61 as shown in FIG. 5C, thereby forming a layered body 63 includingthe positive electrode plate 20, a solid electrolyte layer 62 and thenegative electrode plate 30 as shown in FIG. 5D (Process (ii)). Thesolid electrolyte layer 62 is formed by solidification of the melt 61.At this time, the positive electrode plate 20 and the negative electrodeplate 30 are compressed so as to form the layered body of the collector21/the active material layer 22/the solid electrolyte layer 62/theactive material layer 32/the collector 31. The solid electrolyte layer62 to be formed has a thickness of about 0.1 μm to 10 μm, for example.This process can be carried out by the cooling rollers 13 and 14 shownin FIG. 1. At this time, it is preferable that the cooling rollers 13and 14 are used to compress the melt 61 while cooling it down via thepositive electrode plate 20 and the negative electrode plate 30. Bycooling down the melt 61 rapidly, it is possible to form the solidelectrolyte layer 62 with excellent crystallinity.

[0043] The obtained layered body 63 is taken up by the take-up roller16. Thereafter, the layered body 63 is cut into a predetermined size andsealed into a case together with a nonaqueous electrolytic solution,followed by lead welding etc., thereby obtaining a lithium secondarybattery. This process can be carried out by a general method.

[0044] In this way, a lithium secondary battery can be manufactured. Inthe manufacturing method of the second embodiment, since the solidelectrolyte layer is formed by spraying, a thin solid electrolyte layercan be formed in a highly productive manner. Moreover, since theformation of the solid electrolyte layer by spraying makes it easier tocontrol the composition of the solid electrolyte layer, it is possibleto manufacture a lithium secondary battery having excellentcharacteristics.

[0045] (Third Embodiment)

[0046] The third embodiment is directed to another example of themanufacturing method for manufacturing a lithium secondary battery,according to the present invention. Although the third embodiment willdiscuss the case of using the manufacturing apparatus 10 a described inthe first embodiment, the manufacturing method of the present inventionis not limited to this. FIGS. 6A to 6D show a manufacturing process inthe third embodiment.

[0047] First, a positive electrode plate 20 a as shown in FIG. 6A and anegative electrode plate 30 a as shown in FIG. 6B are prepared.

[0048] The positive electrode plate 20 a includes a collector 21 andactive material layers 22 formed on both surfaces of the collector 21.The collector 21 and the active material layers 22 can be thosedescribed in the second embodiment. The positive electrode plate 20 acan be formed by applying or depositing a material of the activematerial layers 22 onto the collector 21. More specifically, it can beformed using the positive electrode plate forming device 40 shown inFIG. 3.

[0049] The negative electrode plate 30 a includes a collector 31 andactive material layers 32 formed on both surfaces of the collector 31.The collector 31 and the active material layers 32 can be thosedescribed in the second embodiment. The negative electrode plate 30 acan be formed by applying or depositing a material of the activematerial layers 32 onto the collector 31. More specifically, it can beformed using the negative electrode plate forming device 50 shown inFIG. 4.

[0050] Next, a melt of a solid electrolyte is ejected toward at leastone electrode plate selected from the positive electrode plate 20 a andthe negative electrode plate 30 a, thereby depositing the solidelectrolyte onto the at least one electrode plate (Process (i)). FIG. 6Cillustrates an example of this Process (i). In the example illustratedin FIG. 6C, a melt 61 is ejected toward and deposited onto both of thepositive electrode plate 20 a and the negative electrode plate 30 a. Themelt 61 can be a melt described in the second embodiment.

[0051] Thereafter, the positive electrode plate 20 a and the negativeelectrode plate 30 a are compressed while sandwiching the melt 61,thereby forming a layered body 63 a including the positive electrodeplate 20 a, a solid electrolyte layer 62 and the negative electrodeplate 30 a as shown in FIG. 6C (Process (ii)). This process is similarto that described in the second embodiment.

[0052] Then, after the melt 61 is ejected toward at least one surface ofthe layered body 63 a, the layered body 63 a is wound by the take-uproller 16, thereby layering the layered body 63 a. In this way, alayered body 64 in which a plurality of the layered bodies 63 a arelayered with the solid electrolyte layers 62 sandwiched therebetween isobtained as shown in FIG. 6D. The layered body 64 can be formed usingthe manufacturing apparatus 10 a. Thereafter, the layered body 64 is cutinto a predetermined size and sealed into a case together with anonaqueous electrolytic solution, followed by lead welding etc., therebyobtaining a lithium secondary battery. This process can be carried outby any suitable method.

[0053]FIG. 7 is a sectional view showing an example of a lithiumsecondary battery manufactured by the manufacturing method of thepresent invention. A lithium secondary battery 70 shown in FIG. 7includes a case 71, a seal 72, the layered body 64, a lead 73 andinsulating plates 74 and 75. The configuration of the lithium secondarybattery 70 is similar to that of general lithium secondary batteries,and members used in general lithium secondary batteries can be appliedto parts other than the layered body 64.

[0054] The case 71 is made of metal and functions as a negativeelectrode terminal. The case 71 is sealed by the seal 72. The seal 72functions as a positive electrode terminal. An electrolytic solution(not shown) is sealed in the case 71.

[0055] The layered body 64 includes the positive electrode plate 20 a,the solid electrolyte layer 62 and the negative electrode plate 30 a.The positive electrode plate 20 a is connected to the seal 72 by thelead 73. The insulating plates 74 and 75 prevent a short circuit betweenthe negative electrode plate 30 a and the seal 72 and that between thepositive electrode plate 20 a and the case 71.

[0056] It should be noted that the lithium secondary battery illustratedin FIG. 7 is an example of a battery manufactured by the manufacturingmethod of the present invention, and the manufacturing method of thepresent invention can be utilized for various other forms of batterymanufacturing.

[0057] The invention may be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof Theembodiments disclosed in this application are to be considered in allrespects as illustrative and not restrictive. The scope of the inventionis indicated by the appended claims rather than by the foregoingdescription, and all changes that come within the meaning and range ofequivalency of the claims are intended to be embraced therein.

INDUSTRIAL APPLICABILITY

[0058] As described above, with a method for manufacturing a lithiumsecondary battery according to the present invention, a thin lithiumsecondary battery with excellent characteristics can be manufactured ina highly productive manner. Further, with a manufacturing apparatusaccording to the present invention, it is easy to carry out themanufacturing method of the present invention.

1. A method for manufacturing a lithium secondary battery comprising apositive electrode plate, a negative electrode plate, and a solidelectrolyte arranged between the positive electrode plate and thenegative electrode plate; the method comprising: (i) ejecting a melt ofthe solid electrolyte onto at least one electrode plate selected fromthe positive electrode plate and the negative electrode plate, therebydepositing the melt onto the at least one electrode plate; and (ii)compressing the positive electrode plate and the negative electrodeplate while sandwiching the melt, thereby forming a layered bodycomprising the positive electrode plate, an electrolyte layer comprisingthe solid electrolyte, and the negative electrode plate.
 2. The methodaccording to claim 1, wherein the solid electrolyte comprises Li₃PO₄. 3.The method according to claim 2, wherein the solid electrolyte isLi₃PO₄, a solid electrolyte obtained by adding nitrogen to Li₃PO₄, orLi₃PO₄—Li₂S—SiS₂.
 4. The method according to claim 1, further comprisingafter the (ii) compressing, (iii) layering the layered body by ejectingthe melt of the solid electrolyte onto at least one surface of thelayered body and then winding the layered body.
 5. The method accordingto claim 1, wherein in the (ii) compressing, the layered body is formedby compressing the positive electrode plate and the negative electrodeplate while cooling them down.
 6. The method according to claim 1,wherein the electrolyte layer has a thickness ranging from 0.1 μm to 10μm.
 7. An apparatus for manufacturing a lithium secondary batterycomprising a positive electrode plate, a negative electrode plate, and asolid electrolyte arranged between the positive electrode plate and thenegative electrode plate; the apparatus comprising: a spraying devicefor ejecting a melt of the solid electrolyte onto at least one electrodeplate selected from the positive electrode plate and the negativeelectrode plate; and a compressing device for compressing the positiveelectrode plate and the negative electrode plate while sandwiching themelt.
 8. The apparatus according to claim 7, wherein the compressingdevice comprises two rollers.